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摘 要 通过分析不同择伐强度下思茅松(Pinus kesiya)天然林乔木种群的生态位、种间联结、种内与种间竞争和群落稳定性, 探讨干扰强度对思茅松天然林乔木种群种间与种内关系的影响。结果表明: (1)择伐干扰改变了大多数乔木树种在群落中的优 势地位, 思茅松优势地位未受影响, 随着择伐干扰强度的增加, 思茅松在群落中的生态位宽度逐渐变大, 在重度干扰的群落 中与红木荷(Schima wallichii)一起成为生态幅度最大的树种。(2)通过种间联结与生态位重叠分析发现, 随着干扰强度的加剧, 乔木种群的种间关系发生变化, 中度干扰群落中物种之间的生态位重叠明显高于未干扰和重度干扰群落, 而在三类群落中, 思茅松与其他种群之间的重叠值较小。随着干扰强度增加, 种群间正联结与负联结的种对所占的比例逐渐增加。(3) Hegyi竞 争指数表明, 三类群落中思茅松种群的竞争压力主要来自种间, 而干扰强度进一步增加了思茅松种群的种间竞争强度, 其种 内平均竞争指数随着对象木胸径的增加而减少。(4)林窗是思茅松种群种间和种内关系变化的主要原因, 三类群落都处于较不 稳定的阶段, 但中度干扰群落的物种丰富度与稳定性都高于未干扰和重度干扰的群落。择伐原则依据森林管理的目的而确定

Seedling,made up of small individuals of woody plant species in the understorey,is an important component of many forests and considered as an important source for natural restoration in forest ecosystems.Simultaneously seedling plays an important role in the regeneration of numerous tree species.Based on space-for-time substitution method,we treated coniferous and broad-leaved mixed forest,secondary monsoon evergreen broad-leaved forest(MEBF),primary MEBF in the same area as three different stages of secondary succession of MEBF.Eight sampling plots representing the three different stages distribute in Caiyanghe nature reserve,surrounding the areas of Meizihu and Xinfang reservoir of Puer,in Yunnan Province,the southwest of China.We investigated seedling regeneration characteristics of woody plants of MEBF during secondary succession by looking at species composition,density,height level and the relationship with environmental factors.Overall,we found 2014 individuals of woody seedlings belonging to 101 species(dominated by understory tree species) in the eight plots covering 144-m2 area.The species richness of tree seedling,shrub seedling and liana seedling were 50,29 and 22 respectively,and their corresponding individuals were 1499,299 and 216.Tree seedling was the main component of woody plant seedling,such as Castanopsis echidnocarpa.Pinus kesiya var.langbianensis are dominant species in coniferous and broad-leaved mixed forest,however,their seedlings rarely appeared in the understory.The pine seedling stages need more light than shade-tolerant species which can conserve seedling bank in understory and waited for appropriate chance to regeneration.The woody plant seedling density of coniferous and broad-leaved mixed forest,secondary and mature MEBF was 183±5.69,240±20.31 and 372.5±4.5 individuals per 18m2.As succession progresses,the density of total woody seedlings,tree seedlings and liana seedlings all increased,while the density of shrub seedlings did not change significantly.Celastrus virens as a liana was particularly conspicuous in mature MEBF.Species richness of liana seedlings tended to increase,while species richness of tree seedlings and shrub seedlings remained relatively stable along the succession gradient.The Shannon-Wiener index of woody seedlings was significantly lower in primary MEBF than those in mixed forest and secondary MEBF.The abundance of woody seedlings in secondary and primary MEBF decreased with the increase of height level,while in mixed forest,the abundance of woody seedlings form a unimodal pattern with peak at 20 cm.Species richness,however,showed consistent(increasing or decreasing) pattern with the increase of height level in all these forest types.Distribution of woody seedlings abundance concentrated in 0—20 cm in the three community types.Woody seedlings species richness of mature MEBF was significantly lower than coniferous and broad-leaved mixed forest when height level was at Ⅰand Ⅱ.Srensen index indicated a close link between tree and liana seedlings and the species composition of the community.Moreover,tree seedling density distribution was significantly negatively correlated with the slope of the plot,while shrub seedling density was significantly positively related to soil pH.